Roast corn over an open burner flame until charred but not burnt, rotating frequently, about 5 min. Cut corn off cob and put kernels into a large mixing bowl. (If using frozen kernels, place defrosted kernels on a baking sheet and roast at 400°F until browned, about 10 min.)

Add diced red onion, cilantro and remaining lime juice to roasted corn and season with salt and pepper.